Heat accumulation segments of the type indicated above are part of axial-flow turbo engines, through which there are flow working media, which are gaseous for the purpose of compression or controlled expansion, and which as a result of their high process temperatures put those system components that are directly acted upon by the hot working media under considerable thermal load. In particular in the turbine stages of gas turbine systems, the rotor blades and guide blades, which are arranged axially one behind the other in rows of rotor blades and guide blades, are directly acted upon by the combustion gases produced in the combustion chamber. To prevent the hot gases that flow through the flow duct also from reaching regions inside the turbo engine that are located remote from the flow duct, so-called heat accumulation segments that are provided on the stator side, in each case between two rows of guide blades arranged axially adjacent to one another, ensure that there is a bridge-like seal, which is as gastight as possible, between the two axially adjacent rows of guide blades.
Heat accumulation segments of corresponding construction may also be provided along the rotor unit. These are to be mounted on the rotor side, in each case between two axially adjacent rows of rotor blades, in order to protect regions inside the rotor from excessive heat input.
Although the statements below refer exclusively to heat accumulation segments arranged between two rows of guide blades, and to this extent make it possible to separate the housing on the stator side and the components associated therewith from the flow duct, which is subject to heat load, and to protect them accordingly, it is also conceivable to provide the measures below in a heat accumulation segment that serves to protect entrained rotor components and that is intended for mounting between two rows of rotor blades arranged axially adjacent to one another.
An arrangement of guide blades that is known per se and has an integrated heat accumulation segment can be seen from the partial longitudinal sectional illustration of FIG. 2. FIG. 2 shows a partial longitudinal section through a gas turbine stage in which a flow duct K is delimited radially internally by a rotor unit 101 and radially externally by a stator unit 102. Rotor blades 103 project radially, in a manner rotationally fixed to the rotor unit 101, into the flow duct K′, through which moreover hot gases flow axially in a direction of flow oriented as indicated by the arrow.
The flow duct K′ is delimited radially externally by guide blades 104 that are mounted on the stator side and whereof the guide blade vanes 141 project radially inward into the flow duct K′. In order to separate the flow duct K′ in gastight manner from the components mounted on the stator side, the guide blades 104 have a platform 142 which, in the form of a one-part component, covers the axial region directly around the guide blade vane 141 and, in the form of a balcony-like overhang 142′, covers the region that bridges two rows of guide blades and radially opposes each of the guide blade tips.
Because the guide blades 104 are arranged in the peripheral direction of the gas turbine, in respective rows of guide blades, those guide blades 104 within a guide blade row that are in each case arranged directly adjacent in the peripheral direction have to be connected to one another in gastight manner along their axial side edges 105. For this there serves a tape seal 106 that runs over the entire extent of the side edge 105 and opens on either side into corresponding grooves along the side edges of two adjacent guide blades. The tape seal 106 ensures in particular that no cooling air that is supplied to the platform 142 on the stator side can escape into the flow duct K′, and hence that corresponding cooling ducts inside the guide blade are available for the effective cooling of all the guide blade regions exposed to the hot gases.
However, everyday operation of gas turbine systems shows that all the components of the gas turbine stage are exposed not only to heat loads but also to mechanical vibrations, as a result of which for example the guide blades 104 are also subjected to tiny radial and axial movements and jolting, and a not inconsiderable result of this is that the tape seals mounted between the guide blades are also weakened. Thus, in the course of mechanical vibrational loads inside the tape seals, cracks and fractures are produced, as a result of which the seals start to become very crumbly. In the event of seal damage of this kind, considerable losses may occur due to leakage between the individual guide blade segments, such that the cooling of the individual guide blades that is required for safe operation cannot be guaranteed sufficiently.
To meet this need, maintenance and inspection work has to be carried out regularly on the guide blades and on the sealants provided in this region. However, this work requires complete rows of guide blades to be dismantled in order ultimately to replace tape seals that are provided between two adjacent guide blades in a guide blade row.
It can be seen, from the joining connection between a guide blade 104 and a stator-side support structure 107 supporting the latter, which can be seen from the longitudinal sectional illustration in FIG. 2, that the guide blade 104 is joined by way of in each case two collar-shaped joining contoured elements 108, 109 that are in engagement with corresponding recesses 110, 111 inside the support structure 107. The individual guide blades 104 can be inserted into the groove-shaped recesses 110, 111 and removed therefrom in the peripheral direction for the purpose of assembly and dismantling. However, if only a single guide blade within a guide blade row is to be inserted into or removed from the arrangement of guide blades, then it is usually necessary for the complete guide blade row or at least segments of the guide blade row to be dismantled.